Lemon-Lime Sheet Cake

1 (18.25 ounce) box lemon cake mix
1 small box lime gelatin

Dissolve gelatin in 3/4 cup boiling water. Add 1/2 cup cold water. Set aside at room temperature.

Bake cake as directed on the package in a 13 x 9-inch pan. Cool cake for 20 minutes.

Poke deep holes through the top of the cake. Pour gelatin mixture over. Refrigerate cake while preparing topping.

Topping
1 large container Cool Whip